Iranian forces 'seize oil tanker, crew'

Iran's paramilitary Revolutionary Guard forces have seized a foreign oil tanker accused of smuggling oil with a crew of 12, Iran's state TV has reported.

The announcement came just days after an oil tanker based in the United Arab Emirates disappeared off trackers in Iranian territorial waters.

The Panamanian-flagged oil tanker MT Riah stopped transmitting its location overnight on Sunday near Qeshm Island, which has a Revolutionary Guard base on it, according to data listed on tracking site Maritime Traffic.

Iran's state television did not identify the seized vessel, but said it was intercepted on Sunday. It said the oil tanker had 12 foreign crew members on board and was involved in smuggling some 1 million litres of fuel from Iranian smugglers to foreign customers.

"The vessel that Iran towed to its waters after receiving a distress call, was later seized with the order from the court as we found out that it was smuggling fuel," the Guards said in a statement quoted by state television.

The report said the oil tanker was intercepted in south of Iran's Larak Island in the Strait of Hormuz.

Oil prices rose about 1 per cent on Thursday following Iran's claims. Brent crude futures were up 48 cents at $US64.14 a barrel by 11:48am GMT after hitting a session high of $US64.46.

West Texas Intermediate crude futures were up 33 cents at $US57.11 after the US benchmark hit a session high of $US57.32.

Britain is seeking further information on the reports Iran has seized a foreign tanker, a government spokeswoman said on Thursday, urging the Iranian authorities to de-escalate tensions.

"We're seeking further information following reports of a tanker seized in the Gulf. We continue to urge the Iranian authorities to de-escalate the situation in the region," the spokeswoman said.

"We are continuously monitoring the security situation there and are committed to maintaining freedom of navigation, in accordance with international law."

A US defence official had told The Associated Press earlier this week that America "has suspicions" that Iran seized the oil tanker when it turned off its tracker in the Strait of Hormuz.

An Emirati official had told the AP the small oil tanker made no distress call before switching off its tracker.

The 58-metre Riah typically made trips from Dubai and Sharjah on the UAE's west coast before going through the strait and heading to Fujairah on the UAE's east coast.

The acknowledgement that a vessel has been seized by Iran's Revolutionary Guard appears to contradict statements by Iran's Foreign Ministry spokesman on Wednesday saying Iran had aided a foreign oil tanker with a malfunction.

The move by the Guard comes amid heightened tensions between Iran and the US after President Donald Trump pulled the United States out of Iran's nuclear deal with world powers last year and imposed sanctions, including on Iranian oil exports.

Iran has recently increased uranium production and enrichment over the limits of its 2015 nuclear deal, trying to put more pressure on Europe to offer it better terms and allow it to sell its crude oil abroad.

The US has sent thousands of additional troops, nuclear-capable B-52 bombers and advanced fighter jets into the Mideast amid the heightened tensions.

Mysterious attacks on oil tankers and Iran shooting down a US military surveillance drone has added to the fears of an armed conflict breaking out.

US Central Command chief General Kenneth McKenzie said it was talking to other countries about freedom of navigation in the Gulf and will work "aggressively" to find a solution to enable free passage.